Method for utilizing fixture having integrated datum locators

ABSTRACT

A fixture adapted to precisely position two components to permit multiple machining operations of the components at a single work station. The fixture includes a backbone having a first portion for securing the first component and a second portion for securing the second component. First and second portions each further include an integral lobe and a finger which extend outwardly from the backbone, each terminating in a datum surface, as well as an additional datum surface which collectively form a set of datum locators along both the first and second portions. Each set of datum locators precisely positions the two components at a predetermined distance and orientation from each other.

BACKGROUND OF THE INVENTION

The present invention relates generally to fixtures having closetolerance datum locators, and more particularly to fixtures havingintegrated close tolerance datum locators used for providing multiplemanufacturing operations on multiple parts at a single manufacturingstation.

In the manufacture of components, especially those machined to closetolerances further having intricate and complex shapes, such as gasturbine engine blades and vanes, tooling fixtures adapted to secure thecomponents are required. Such fixtures, which represent a manufacturingstation, typically contain three reference contact surfaces machined toeven closer tolerance, referred to as datums, to precisely position andsecure the component for the manufacturing step that is performed at themanufacturing station. Multiple stations are usually required tomanufacture the component, typically one station is required for eachmanufacturing step. Although closer datum tolerances may be maintainedin the fixtures, additive tolerance build-up is almost invariablyintroduced at each of the manufacturing stations resulting in componentshaving increased dimensional deviation from that desired. Minimizing thenumber of fixtures required to manufacture the component is desirabledue to component tolerance build-up and the high cost associated withfixture fabrication.

What is desired is an integral fixture at a single manufacturing stationhaving at least two sets of close tolerance datum surfaces that cansecure at least two parts for simultaneous multiple machiningoperations.

SUMMARY OF THE INVENTION

This invention pertains to a fixture adapted to precisely position atleast two components at a predetermined distance and orientationtherebetween for permitting a machining means directed along the fixtureto simultaneously perform at least one machining operation to the atleast two components. The fixture incorporates a backbone having a firstportion for securing a first component and a second portion for securinga second component. The first and second portions each further includingan integral set of three precisely positioned datum surfaces formedtherein for precisely positioning the first and second components.

An advantage of the present invention is that it provides a fixture thatreduces component tolerance build-up introduced during the manufactureof components due to reduction of the number of fixtures required.

A further advantage of the present invention is that it provides afixture that reduces the number of manufacturing stations required tomanufacture a component.

Still another advantage of the present invention is that it provides afixture that reduces the number of machining tools required tomanufacture a component.

Yet another advantage of the present invention is that rework ofout-of-tolerance articles is reduced.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention. Amongthe advantages and objects of the present invention is to provide afixture adaptable for multiple components to reduce the number offixtures required for manufacture of components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a fixture of the present invention securingtwo components for manufacture;

FIG. 2 is a perspective view of the fixture in FIG. 1;

FIG. 3 is a back view of the fixture in FIG. 1;

FIG. 4 is a perspective view of a first manufacturing sequence whereinthe fixture is securing one component;

FIG. 5 is a perspective view of a subsequent manufacturing sequencewherein the fixture is securing two components; and

FIG. 6 is a perspective view of a still subsequent manufacturingsequence wherein the fixture is securing two components.

FIG. 7 is a front view of an alternate embodiment of a fixture of thepresent invention securing components for manufacture.

Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIG. 1 illustrates a front view of thepreferred form of the invention, wherein 10 generally designates afixture constructed in accordance with and embodying the presentinvention. Fixture 10 represents a single manufacturing station andincludes a backbone 12 having a first portion 14 and a second portion 16for positioning a first blade 38 and a second blade 40, respectively,therein. First portion 14 includes datum surfaces 26, 30 and 34 toprecisely position first blade 38, and second portion 16 includes datumsurfaces 28, 32 and 36 to precisely position second blade 40 inpreparation of multiple machining operations at a single manufacturingstation as will be discussed in more detail below.

Referring to FIGS. 1 and 2, fixture 10 includes a proximal end 11 forsecuring fixture 10 at its respective manufacturing station while blades38, 40 are being machined. Adjacent proximal end 11 along first portion14 a lobe 22 extends outwardly from backbone 12. Lobe 22 terminates atdatum surface 34 which contacts and precisely positions a base 50, alsoreferred as dovetail, of first blade 38. Further proceeding alongbackbone 12 in a direction toward its distal end 13, a finger 18 extendsoutwardly from a front face 15 that is opposite that of back face 17 ofbackbone 12 and further extends outwardly from backbone 12 along firstportion 14, terminating at datum surface 30, which contacts andprecisely positions a vent portion 46 of first blade 38. Furtherproceeding along backbone 12 in a direction toward distal end 13, datumsurface 26 which is located adjacent distal end 13 along first portion14 contacts and precisely positions a shroud 42 of first blade 38. Oncefirst blade 38 is collectively positioned against datum surfaces 26, 30and 34, a clamping means (not shown) secures first blade 38 in thisposition during manufacturing operations at this station.

Second portion 16 of backbone 12 shall now be discussed. Adjacentproximal end 11 along second portion 16 of backbone 12 is located datumsurface 28 which contacts and precisely positions a shroud 44 of secondblade 40. Further proceeding along backbone 12 in a direction towarddistal end 13, a finger 20 extends outwardly from front face 15 ofbackbone 12 and further extends outwardly from backbone 12 along secondportion 16, terminating at datum surface 32, which contacts andprecisely positions a vent portion 48 of second blade 40. Furtherproceeding along backbone 12 in a direction toward distal end 13,adjacent distal end 13 along second portion 16 is located a lobe 24 thatextends outwardly from backbone 12. Lobe 24 terminates at datum surface36 which contacts and precisely positions a base 52 of second blade 40.Once second blade 40 is collectively positioned against datum surfaces28, 32 and 36, a clamping means (not shown) secures second blade 40 inthis position during manufacturing operations at this station.

In the preferred embodiment, first and second blades 38, 40 areidentical parts. Similarly, datum surfaces 26, 30 and 34 each correspondto datum surfaces 28, 32 and 36. That is to say, collectively, each ofthese sets of datum surfaces contacts and precisely positions theidentical portions of first and second blades 38, 40 at a predeterminedspacing and orientation from each other. Each blade 38, 40 includes anaxis 54, 56 which spans the center of the blade from dovetail 50 toshroud 42. The difference in orientation between first blade 38 andsecond blade 40 is that second blade 40 is rotated 180 degrees about itsaxis 56 with respect to first blade 38 that passes through the middle ofsecond blade 40. This orientation is apparent by inspection of theorientations of first blade 38 and second blade 40 in FIGS. 1-3.Similarly, by rotating first blade 38 180 degrees about a first axis 54that passes through the middle of first blade 38, first blade 38 matchesthe orientation of second blade 40.

Utilizing advances in tool forming methods, such as wire electrodischarge machining (“EDM”) which uses a spool of wire, typically brass,fixture 10 is shaped by vaporizing a desired path along the profile offixture 10 to form integral datum surfaces 26, 28, 30, 32, 34 and 36,each datum surface having tolerances of +/−0.0001 of an inch from thenominal position. This high degree of precision permits multiple sets ofdatum surfaces to be integrated onto a single fixture withoutintroducing tolerance build-up and further provides substantial costsavings, both as previously discussed.

A method permitting multiple machining operations to be performed at asingle manufacturing station shall now be discussed. For purposes ofFIGS. 4-6, designations A, B and C represent three identical bladesintroduced sequentially into fixture 10 at different times during themanufacturing process. Designations A′ and B′ represent blades A and B,respectively, rotated 180 degrees from the orientation as initiallyinstalled in first portion 14 of fixture 10, as previously discussed.

Referring now to FIG. 4, an operator (not shown) installs blade A, whichincludes positioning and securing blade A along first portion 14 offixture 10 against datum surfaces 26, 30 and 34 with at least oneclamping means (not shown). Typically, clamping means include at leastone set of arms controllably actuated by hydraulic, pneumatic, springretention or any number of other mechanical arrangement providing acontrollable compressive force to opposed sides of blade A and backbone12 fixture 10 so that blade A and fixture 10 are directed toward oneanother to ensure that blade A is located against the respective datumsurfaces 26, 30 and 34 of the first portion 14 of the fixture 10. Twosets of clamping means are typically employed to locate and secure bladeA in position against datum surfaces 26, 30 and 34. Ahydraulically-powered clamping means actuated by the use of highpressure hydraulic fluid is preferably employed to locate and secure theportion of blade A adjacent shroud 42 against datum surfaces 26 and 30due to the ability of the clamping means to apply elevated levels ofcompressive forces. Such elevated compressive forces are required toimmobilize this portion of blade A with respect to datum surfaces 26 and30, since these datum surfaces are adjacent shroud 42 which is machinedas discussed below. In other words, the clamping means must exertsufficient compressive forces between datum surfaces 26 and 30 and blade38 to withstand the reactive forces created by the machining of shroud42. Similarly, a second clamping means is preferably employed tolikewise locate and secure base 50 against datum 34. However, since adecreased level of compressive forces are required to immobilize base 50against datum 34, as compared to clamping means actuated by pneumatics,providing a lower range of compressive forces than hydraulicallyoperated clamping means, or a spring retention clamping means, whichtypically provides a range of compressive forces less than pneumaticallyoperated clamping means, may alternately be used.

Once blade A is secured, machining means 58, such as a grinding wheel,is directed toward fixture 10 along a travel direction 60 so that amachining portion 62 formed in machining means 58 performs a machiningoperation on a base 66 of blade A. Upon completion of the machiningoperation to base 66, the operator opens clamping means securing blade Aand removes blade A from first portion 14. The operator then rotatesblade A 180 degrees as previously discussed so that blade A now becomesblade A′ and installs blade A′ as shown in FIG. 5, which includespositioning and securing blade A′ along second portion 16 of fixture 10against datum surfaces 28, 32 and 36 with clamping means as previouslydiscussed. In addition, operator installs blade B along first portion 14of fixture 10 in a similar manner to installing blade A along firstportion 14 of fixture 10.

Referring again to FIG. 5, once blades A′ and B have been installed infixture 10, machining means 58 is again directed toward fixture 10 alongtravel direction 60 so that simultaneous machining operations areperformed to both blades A′ and B. Machining portion 62 performs amachining operation on a shroud 68 of blade B, and a machining portion64 formed in machining means 58 performs a machining operation on a base70 of blade A′.

Referring to FIGS. 5 and 6, once the machining operation to shroud 70 ofblade A′ and base 68 of blade B has been completed, operator opensclamping means securing blade A′, removes blade A′ from second portion16, and sets blade A′ aside for subsequent manufacturing operations at adifferent manufacturing station, if required. Operator then opensclamping means securing blade B along first portion 14, removes blade Bfrom first portion 14, rotates blade B 180 degrees as previouslydiscussed, wherein blade B now becomes blade B′, and installs blade B′along second portion 16 of fixture 10. Finally, operator installs bladeC along second portion 14 of fixture 10.

Once blades B′ and C have been installed in fixture 10, machining means58 is again directed toward fixture 10 along travel direction 60 so thatsimultaneous machining operations are performed to both blades B′ and C.That is, machining portion 62 performs a machining operation on a shroud72 of blade C, and machining portion 64 performs a machining operationon a base 74 of blade B′. Additional blades can be machined utilizingthis method.

Although first and second blades 38, 40 are the same part in thepreferred embodiment, it is apparent to one skilled in the art thatthese components need not be identical. That is to say, it may bepossible to further add datum surfaces along first and second portions14, 16 of backbone 12 to additionally accommodate blades of differentlengths, preferably configured for machining operations utilizing thesame machining means 58. For example, referring to FIG. 7, an alternateembodiment of fixture 110 has all the features of fixture 10, but has anadditional set of datum surfaces for first portion 114 and secondportion 116. The additional sets of datum surfaces and associatedfeatures are differentiated from the surfaces and features of fixture 10by the addition of a “1” digit to the left of the originally identifiedfeatures for fixture 10. In other words, datum surfaces 126, 130 and 134of a first portion 114 accommodate a first blade 138 which is longerthan blade 38, and similarly, data surfaces 128, 132 and 136 of a secondportion 116 accommodate a second blade 140, which is identical to blade138. Similarly, although the present invention is directed to fixturesfor securing turbine rotor blades, it is apparent that any number ofcomponents capable of being located by datum surfaces may be employed.Additionally, while the present invention is directed to a machiningmeans such as a grinding wheel, any cutting blades, abrasives, highpressure fluid cutting streams, high temperature or high energy cuttingbeams or any other manufacturing methods that can be utilized to effectshaping of a component is contemplated. Further, although the preferredembodiment secures first and second blades at a predetermined spacingand orientation 180 degrees with respect to each other, there may becomponent geometries that may utilize a different orientation. Moreover,although the preferred embodiment is directed to a fixture securing twocomponents, it is apparent that the fixture could be configured toaccommodate more than two components by either widening the fixture toadditionally include, for example, third and fourth portions to securethird and fourth components, respectively, or to “piggy back” a secondfixture substantially identical to the first fixture (the fixture of thepresent invention) wherein the first and second fixtures are integralwith respect to each other and aligned to receive machining means 58.Finally, it is apparent that regarding the method for employing thepresent invention, the order of installation and/or removal of thecomponents from the fixture by the operator, or by an automated systemis not critical and may be performed in any order so long as thecomponents are secured prior to the machining process.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A method for simultaneously performing at least one manufacturingoperation to each of at least two components utilizing a single fixture,the method comprising the steps of: providing a fixture having abackbone further having a first portion for securing a first componentthereto and a second portion for securing a second component thereto; atleast three immobile precisely positioned datum surfaces formed on eachof the first portion and the second portion; the datum surfaces of thefirst and the second portions corresponding to each other and to datumsurfaces of the first and second components; securing datum surfaces ofthe first component to the at least three precisely positioned datumsurfaces on the first portion; securing datum surfaces of the secondcomponent to the at least three precisely positioned datum surfaces onthe second portion; and directing a manufacturing means along thefixture to simultaneously perform at least one manufacturing operationto each of the first and second components of the at least twocomponents along the fixture.
 2. The method of claim 1 wherein themanufacturing means is at least one cutting blade.
 3. The method ofclaim 1 wherein the manufacturing means is a high pressure fluid cuttingstream.
 4. The method of claim 1 wherein the manufacturing means is ahigh energy cutting beam.
 5. The method of claim 1 wherein thecomponents are identical.
 6. The method of claim 1 wherein thecomponents are gas turbine engine blades.
 7. The method of claim 1wherein the components are gas turbine engine vanes.
 8. The method ofclaim 1 wherein the manufacturing means is a grinding wheel.
 9. Themethod of claim 1 wherein the providing, securing and directing stepsincluding the steps of: providing a fixture having a backbone furtherhaving a third portion through a corresponding portion for each securinga corresponding third component through a corresponding componentthereto; at least three precisely positioned datum surfaces formed oneach of the third portion through the corresponding portion; the datumsurfaces of the third portion through the corresponding portioncorresponding to each other and to datum surfaces of the correspondingthird component through corresponding component; securing each of thethird component through corresponding component to the at least threeprecisely positioned datum surfaces on the corresponding third portionthrough corresponding portion; and directing a manufacturing means alongthe fixture to simultaneously perform at least one manufacturingoperation to each of the third through corresponding components of theat least two components along the fixture.
 10. A method for performingat least two manufacturing operations to at least two substantiallyidentical components utilizing a single fixture, the method comprisingthe steps of: providing a fixture having a backbone further having afirst portion for securing a component in a first position thereto and asecond portion for securing the component previously secured to thefirst portion, the second portion for securing the component in a secondposition thereto; at least three immobile precisely positioned datumsurfaces formed on each of the first portion and the second portion; thedatum surfaces of the first and the second portions corresponding toeach other and to datum surfaces of the components; securing datumsurfaces of a first component in the first position to the at leastthree precisely positioned datum surfaces on the first portion;directing a manufacturing means along the fixture to perform at leastone manufacturing operation to the first component along the fixture;removing the first component from the first portion; securing datumsurfaces of the first component in the second position to the at leastthree precisely positioned datum surfaces on the second portion;securing datum surfaces of a second component in the first position tothe at least three precisely positioned datum surfaces on the firstportion; directing the manufacturing means along the fixture tosimultaneously perform at least one manufacturing operation to each ofthe two components of the at least two components along the fixture. 11.The method of claim 10 wherein the first position of the first andsecond components is oriented substantially 180 degrees with respect tothe second position.
 12. The method of claim 10 wherein themanufacturing means is at least one cutting blade.
 13. The method ofclaim 10 wherein the manufacturing means is a high pressure fluidcutting stream.
 14. The method of claim 10 wherein the manufacturingmeans is a high energy cutting beam.
 15. The method of claim 10 whereinthe components are gas turbine engine blades.
 16. The method of claim 10wherein the components are gas turbine engine vanes.
 17. The method ofclaim 10 wherein the manufacturing means is a grinding wheel.
 18. Themethod of claim 10 wherein the providing, securing and directing stepsincluding the steps of: providing a fixture having a backbone fartherhaving a third portion through a corresponding portion for each securinga corresponding third component through a corresponding componentthereto; at least three precisely positioned datum surfaces formed oneach of the third portion through the corresponding portion; the datumsurfaces of the third portion through the corresponding portioncorresponding to each other and to datum surfaces of the correspondingthird component through corresponding component; securing each of thethird component through corresponding component to the at least threeprecisely positioned datum surfaces on the corresponding third portionthrough corresponding portion; and directing a manufacturing means alongthe fixture to simultaneously perform at least one manufacturingoperation to each of the third through corresponding components of theat least two components along the fixture.
 19. A method forsimultaneously performing at least one manufacturing operation to eachof at least two components utilizing a single fixture, the methodcomprising the steps of: providing a fixture having a backbone furtherhaving a first portion through a corresponding portion for each securinga corresponding first component through a corresponding componentthereto; at least three precisely positioned datum surfaces formed oneach of the first portion through the corresponding portion; the datumsurfaces of the first portion through the corresponding portioncorresponding to each other and to datum surfaces of the correspondingfirst component through corresponding component; securing each of thefirst component through corresponding component to the at least threeprecisely positioned datum surfaces on the corresponding first throughcorresponding portion; and directing a manufacturing means along thefixture to simultaneously perform at least one manufacturing operationto each of the first through corresponding components of the at leasttwo components along the fixture.